LintCode: Identical Binary Tree

C++

 /**
  * Definition of TreeNode:
  * class TreeNode {
  * public:
  *     int val;
  *     TreeNode *left, *right;
  *     TreeNode(int val) {
  *         this->val = val;
  *         this->left = this->right = NULL;
  *     }
  * }
  */
 class Solution {
 public:
     /**
      * @aaram a, b, the root of binary trees.
      * @return true if they are identical, or false.
      */
     bool isIdentical(TreeNode* a, TreeNode* b) {
         // Write your code here
         if (a == NULL && b == NULL) {
             return true;
         }
         if (a == NULL || b == NULL) {
             return false;
         }
         if (a->val != b->val) {
             return false;
         }
         return isIdentical(a->left, b->left) && isIdentical(a->right, b->right);
     }
 };